Transmission for outboard motors



April 4, 1933- O J. P. LANDRUM 1,903,350

TRANSMISSION FOR OUTBOARD MOTORS Filed June 20, 1932 2 Sheets-Sheet l INVENTOR J- B Landrum ATTO RNEYS April 4, 1933. J. P. LANDRUM 1,903,

TRANSMISSION FOR OUTBOARD MOTORS I Filed June 20, 1932 2 Sheets-Sheet 2 INVENTOR JP- La'ndrum ATTQRNEYS 20 fuel and lubricant consumed Patented Apr. 4, 1933 UNITED STATES PATENT oFFIe JOHN P. LANDRUM,' OF BIRMINGHAM, ALABAMA TRANSMISSION non Application filed June 20,

My invention relates to outboard motors, and has for its object the provision of a means'for transmitting power from the motor to the propeller, which shall be simple and rugged of construction, shall greatly reduce the projected area of the transmission housing, as compared with practice heretofore known to me, and shall in consequence provide for a marked increase in speed of the boat to which it is applied, per unit of power consumed.

My invention is particularly adapted for use with modern high powered motors, ranging in power from 12 to 60 horse power and 15 turning at the rate of from 4,500 to 6,500 revolutions per minute. My invention contemplates a transmission system whereby the useful work performed by such motors may be greatly increased, and a marked saving'in per unit of work performed. 7

in the design of transmission systems for outboard motors there have been well recognized limitations. Among these limitations 23 are, that the propeller tip speed should not exceed 11,000 feet per minute, for the reason 7 that beyond that speed, cavitation sets in, as well as the fact that at the high tip speeds the torsional resistance of the propeller greatly increases. Inasmuch as the economical speed to light powered motors is such that, if directly driven, the tip speed of the propel ler would greatly exceed the critical, it becomes necessary to interpose a gear reduction 1335 between the motor and the p1'0pe Shaft- With outboard motors, it is also well understood that the motor is mounted on the upper end of the transmission system out of the water, and that there is necessarily a vertical 40 shaft with a surrounding housing extending downwardly from the motor which transmits its power through suitable gearing to the propeller shaft. It is necessary that this shaft beof a minimum diameter capable of transmitting the power developed or else the pro- C has heretofore been impractical to place a OUTBOARD morons 1932. Serial No. 618,252.

gear reduction at the upper end of the vertical shaft for the reason that it imposed an undue load on theshaft between the motor and the propellershaft which would necessitate a larger vertical shafta-nd a larger housing. It has accordingly been thecustom to drive the vertical shaft directly from the motor anclplace a gear reduction unit at the lower endof the shaft, between it and the propeller shaft. This necessity of placing a gear reduction unit at the lower end of the vertical shaft necessitated a relatively large housing around the gear reduction unit, the project ed area of which was such as to add undue re- ,7 w sistance to the passage of the boat through the water, though this resistanceis less'than would be imposed by a shaft and housing large enough to sustain the full load on the propeller shaft. 1

The effect of variations in the projected area of the submerged portion of an outboard motor unit may be appreciated from the fact that it has been; found in actual racing tests, a decrease in diameter of the submerged portion of as little as one-half inch, '7 increases the speed of the boat two or three miles per hour. In accordance with my invention, I am enabled to reduce the projected area of the submerged portion of the unit around 60% and the diameter of the submerged portion, as compared with well known makes of such apparatus, around one and one-quarterinches. I

With this improvement, I have found that the speed of theboat towhich it is attached is increased as much as 15% with the same consumption of power and withca consequent saving in fuelper unit of useful work performed. In an actual test, and employing a 7 standard make of sixteen horse power motor with standard transmission system, the maximum speed developed with the boat to which it was applied was 42miles per hour. When this transmission unit was exchanged for one made in accordance with my invention,

the speed increased to 49 miles per hour with of power developed by the the operation of the motor as a whole are brought about in accordance with my invention by employing two parallel vertical shafts mounted one behind the other with respect to the direction of propeller thrust and providing a gear train at the upper ends of the shafts for transmitting the power from the motor to the shafts. This permits dividing the load on the vertical shafts, permits using shafts of much smaller diameter and with a consequent decrease in the projected area of the housing, and due to the fact that the load is divided, the necessary gear reduction between the motor and the propeller may be made at the upper end of the vertical shafts where they are out of the water.

At the lower end-of these vertical shafts there needbe no speed reduction and small bevelled gears may be employed to transmit the power in a 1 to 1, ratio to'the propeller shaft, thereby permitting the use of a gear housing much smaller in projected area than has heretofore been employed. The

' arrangement of the vertical shafts one be- Referring to the drawings for a better understanding of my invention, I show a motor shaft 10 which is positioned in an upper housing 11 depending from the motor (not shown). The lower end of the motor shaft 10 is provided with a ball bearing 15 and beyond it a spur gear 12. The ball bearing 15 is positioned in an intermediate housing 13 secured to the upper housing 11 by means of bolts 14 and 16.

Beneath the intermediate housing 13 is a lower unit housing 17 secured to the intermediate housing by bolts 18 and 19. Positioned in the lower housing 17 are a pair of intermediate vertically disposed shafts 21 and 22. The shafts 21 and 22 are provided with upper ball bearings 23 and 24 and lower ball bearings 26 and 27. At the upper ends of the shafts 21 and 22 are spur gears 28 and 29 having a tooth ratio with respect to the gear 12, such as to give the desired speed reduction between the motor shaft 10 and the intermediate shafts. I

;At the lower end of the lower unit housing 17 is a propeller shaft housing 31 in which is located a propeller shaft 32 mounted in ball bearings 33 and 34. Mounted on the propeller shaft 32 are a pair of bevelled gears 36 and 37 which mesh with similar bevelled gears 38 and 39, preferably in a 1 to 1 ratio, which gears are mounted on the lower ends of the intermediate shafts 21 and 22. shaft 32 is the usual propeller 41 which is protected by a skeg 42. An anti-cavitation plate 43 is arranged upon the lower housing 17' above the propeller 41.

The propeller shaft housing 31 is secured to the lower housing 17 by means of a single bolt 44 extending downwardly through the housing from a socket 46 beneath the lower end of the motor shaft 10. A bolt head 47 on the bolt 44 is accessible through the socket 46 in assembling the transmission system. The lower end of the bolt 44 is threaded at 48 to screw into a suitable threaded recess 49 provided in the propeller shaft. housing 31. Dowels 51 and 52 prevent relative turn-' ing between the propeller shaft housing and T the housing 17.

As may be seen in Fig. 3 the arrangement of the intermediate shafts 21 and 22 is one behind the other in the direction of'thrust of the propeller 41. This permits a narrow housing, stream lined in cross section, as shown in Fig. 3. Theload being divided between the two shafts 21 and 22 permits the use of relatively small shafts and this greatly narrows the width of the housing 17, greatly. reducing its projected area. The propeller shaft housing, enclosing as it does the small bevelled gears 36 and 37, is also stream lined in cross section, and the small gears permit a minimum of proi jected area in the design of said housing. t will be apparent that this design of transmission affords a minimum resistance to translational movement of the boat to which it is attached, and is effective in providing a maximum of economies in fuel consump tion and lubricant. The disposal of the intermediate shafts and the balancing ofthe load also permits the assembly of the unit with the single bolt 44 and the dowels 51 and 52, making it very easily and sturdily built up. I

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof. and I desire, therefore, that only such limitations shall be placed thereupon as On the outer end of the propeller of the drawings, 7

allel vertically disposed intermediate shafts water line, and other gear means between the intermediate shafts and the propeller shaft.

2. In an outboard motor transmission, a 7

motor shaft, a propeller shaft, a pair of parallel vertically disposed intermediate shafts arranged one behind the other in the direction of thrust of the propeller shaft, speed reduction means between the motorshaft and the upper ends of the intermediate shafts, and gear means between the intermediate shafts and the propeller shaft.

3. In an outboard motor transmission, a horizontal propeller shaft, a pair of bevel gears on the propeller shaft, a pair of vertically disposed intermediate shafts arranged one behind the other in the direction of thrust of the propeller shaft and extending above the water line, bevel gears "on the lower ends of the intermediate shafts meshing with the gears 011 the propeller shaft, a motor shaft, and a reduction gear means between the upper ends of the intermediate shafts and the motor shaft.

4. In an outboard motor transmission, a horizontal propeller shaft, a pair of bevel gears on the propeller shaft, a pair of vertically disposed intermediate shafts arranged one behind the other in the direction of thrust of the propeller shaft and extending above the water line, bevel gears on the lower ends of the intermediate shafts meshing with the gears on the propeller shaft, a motor shaft, a reduction gear means between the upper ends of the intermediate shafts and the motor shaft, a housing for the intermediate shafts, stream lined in cross section, a housing for the propeller shaft also stream lined in cross section, and a single bolt for joining the propeller shaft housing to the intermediate shaft housing and disposed between the vertical shafts. v

In testimony whereof I afiix my signature.

JOHN P. LANDRUM. 

